This invention relates to the separation of reaction products and of active catalysts from hydrocarboxylation reaction mixtures. More particularly, the present invention relates to the separation of oxygenated cyanocompounds and of active cobalt and/or ruthenium carbonyl catalysts, with promoters, from hydrocarboxylation reaction mixtures.
Conventional methods of separating reaction products and reaction catalysts from reaction mixtures include distillation and catalyst precipitation. The major products from the hydrocarboxylation of nitriles, that is, oxygenated cyanocompounds, have very high boiling points with respect to the hydrocarboxylation catalysts, generally cobalt and/or ruthenium carbonyl, which are rather heat sensitive. To separate these products by distillation would cause the deactivation and degradation of a significant portion of the catalyst present in the reaction mixture. The catalyst would then require reformation and reactivation before it could be recycled for further use in the reaction. The separation of reaction products by precipitation of catalysts also results in the necessity of reactivating the catalyst before recycle.
U.K. Pat. No. 1,344,669; U.S. Pat. Nos. 3,856,832 and 4,041,057 disclose the extraction of the ester product of a cobalt catalyzed hydroesterification reaction using a hydrocarbon having a boiling point above 70.degree. F. resulting in an ester-containing hydrocarbon phase, and a catalyst-containing alkanol phase. A pyridine promoter is present in both phases, and the catalyst is in an active form for recycling.
Japanese patent application No. 75 62,888 discloses the recovery of catalysts used in esterification of alcohols with olefins and carbon monoxide by the addition of aliphatic hydrocarbons to the reaction mixture. U.S. Pat. No. 3,996,164 discloses the separation of pyridine- and substituted pyridine-promoted cobalt carbonyl complexes from hydroesterification media by cooling a hydrocarbon-containing mixture below 80.degree. C. such that the catalyst utilized becomes insoluble and can be separated.
It has been found that when alcohol solvents are used in the reaction mixtures from the hydrocarboxylation of nitriles to form oxygenated cyanocompounds, the conjugate phase separation of the cyanoproduct from the reaction mixture and catalyst is impractical due to the cyanoproduct being more miscible in the alcohol solvent, than in the hydrocarbon extractant.